* Wolfgang Weisselberg wrote:
> Troy Piggins <usenet-0805@[EMAIL PROTECTED]
> wrote:
>
>> I've had a bit of an edit of it. It's 3504x2336px full size, the
>> crops are smaller obviously.
>
>> I understand that photo quality prints are around 300ppi,
>
> That's for 4x6 (where you get up close to see every detail)
> and other formats where you want to get *really* close up.
>
> Posters usually work out well at 150dpi --- many printers
> (posters are printed, not exposed (e.g. by a laser) and
> chemically developed) can't do more.[1]
>
> Canvas has a surface structure. That structure also limits how
> close you can come to the canvas and expect additional details.
>
>> But I think he really wants this thing blown up, like 1 metre
>> wide or something. I'm concerned it may come out pixelated or
>> something.
>
>> Will it?
>
> 3000 pixels at 1 metre work out to 3 pixel/mm, or ~76 dpi.
> A 20/20 vision resolves reliably 1 arc minute (of black-white
> contrast), or 3 pixel/mm from 1 metre distance.
>
> For something to look pixelated, you need to be able to:
> - see individual pixels as an area
> - see a border where a change happens between individual
> pixels.
> Neither is given at 1 metre and 20/20 vision.
>
> At 20-30cm you might see pixelation if the printer uses a nearest
> neighbour interpolation (which I'd consider incompetent) and you
> have hard contrasts between pixels; with smoother interpolations
> (say, bicubic) you may notice some hard contrasts looking slightly
> blurry, but shouldn't notice pixelation.
>
> If you get much closer, the structure of the canvas will take over,
> limiting resolution and giving the eye 'grip' even on otherwise
> featureless areas, giving a stronger impression of sharpness
> (you can also see that phenomenon with (artificial) film grain).
>
> So, no, I'd not be overly concerned.
>
>> If so, can I scale the image up and do something so that it
>> doesn't print pixelated? Maybe blur it slightly to take out
>> pixelation?
>
> If you need to, ask the printer for the exact pixel size he'll use,
> then upscale on your own and check on 100% view.
>
> I'd assume the printer knew his tools and thus did the upscaling
> and sharpening exactly as needed to get the best out of *his*
> medium, while I'd not know.
>
> -Wolfgang
>
> [1] Printers may deliver very high dpi.
> But even the most expensive ones only have a handful of colour
> shades (e.g. black, photo-black, gray, light-gray, cyan,
> light-cyan, magenta, light-magenta, yellow). So they have to
> dither to get all the shades a photo has. Thus even 16x16
> (==256) dpi may give just 1x1 ppi ...
Thanks for the very detailed explanation Wolfgang. I'll file all
that for future reference :)
--
Troy Piggins
I always appreciate critique.
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